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CD34 expression in desmoplastic melanoma
M P Hoang1, M A Selim, R C Bentley
1Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9073, USA. mai.hoang@UTSouthwestern.edu
Journal of Cutaneous Pathology
|December 12, 2001
Summary
Malignant melanoma can mimic dermatofibrosarcoma protuberans (DFSP), even expressing CD34. This case highlights the importance of immunohistochemical analysis for accurate diagnosis of challenging soft tissue tumors.
Area of Science:
- Oncology
- Dermatopathology
- Surgical Pathology
Background:
- Malignant melanoma can present with diverse histologic features.
- Metastatic melanoma can mimic various soft tissue neoplasms.
- Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue tumor characterized by specific cellular morphology and CD34 expression.
Purpose of the Study:
- To report an unusual case of metastatic malignant melanoma that histologically and immunohistochemically resembled DFSP.
- To highlight the diagnostic challenges posed by melanoma mimicking other spindle cell tumors.
- To emphasize the utility of a comprehensive immunohistochemical panel in differentiating challenging neoplasms.
Main Methods:
- Histopathologic examination of a metastatic melanoma presenting as a soft tissue mass.
- Immunohistochemical staining for CD34, S-100 protein, tyrosinase, HMB-45, and MART-1.
- Electron microscopy to identify melanosomes.
Main Results:
- The tumor exhibited morphologic features closely simulating DFSP, with intersecting fascicles of spindle cells.
- Neoplastic spindle cells demonstrated strong CD34 expression.
- Epithelioid components showed positivity for S-100 protein and tyrosinase, with focal melanin pigment.
- Tumor cells were negative for HMB-45 and MART-1, and melanosomes were absent on electron microscopy.
Conclusions:
- Malignant melanoma can exhibit a striking resemblance to DFSP, both morphologically and immunohistochemically.
- CD34 expression in melanoma, though rare, can occur and contribute to diagnostic confusion.
- A broad panel of immunohistochemical markers is crucial for accurate diagnosis in cases of suspected soft tissue tumors with ambiguous features.